JB Weld or Hi Temp RTV silicone oil crack fix.

The Franklin engine I rebuilt came with an odd ball cast aluminum oil
pan with a big shaft access hole in back. May have been a helicopter
engine oil pan. I put a disc there and welded it shut (from outside).
But the weld is dripping some oil especially when hot. I
am planing to take out the oil pan and fill the inside groove between
the disc and oil pan with either JB weld or Hi Temp RTV silicone.
The RTV works great as gasket to seal out other holes with plates
bolted on them. But there would be no pressure plate to hold it in the
groove in this case. Which one is better choice? Another sealer?

I don’t want to get another oil pan since I adapted this shape
for other uses.

The best material available for this type of repair is BELZONA (1111)
Super metal.
The Belzona technical consultants are very helpful.
The Belzona website is www.belzona.com
I once sealed a 90′ long pourous welded seam on an unleaded gasoline
storage tank at a refinery with Belzona. Caterpiller specs Belzona
for repairs to engines. I have seen several aircraft engines repaired
with Belzona.
Degrease the area to be repaired with MEK. Use a propane torch to
lightly heat the surface. This will bring oils to the surface.
Degrease the area again. Roughen the surface. Ideally, grit blast
with black beauty, to produce a near white 3 mil finish. Degrease.
Apply Belzona Super Metal. Enjoy a dry engine.
This stuff works very well when repairing fuel tank leaks. DO NOT USE
FLAME ON FUEL TANKS, unless you want to make the Darwin list.

Garyplewa 2009-08-20 15:27:23

Use JB Weld! The regular type NOT the quick hardening stuff. Make sure
the area is oil free and cleaned with MEK or Carb Cleaning solvent. I’ve
sealed several oil leaks this way when it was not feasable to remove and
re-weld an oil tank. Years later it is still dry as a bone. JB Weld
is advertised good to 600 F. RTV in my experience tended to pull away on
a scab patch type of repair and leak after a while.

Gary P

Jfleisc 2009-08-20 15:27:29

Is this stuff fuel proof? Can a fuel tank leak be sealed the same way from the
outside?

Jim

Garyplewa 2009-08-20 15:28:44

I don’t know. I’ve only used it for oil leaks which would have otherwise
required engine removal or case splitting. Mind you these were nuisance
leaks not major gushers. So far the JB Weld has held up without leaking.

For a fuel tank I would use Pro-Seal as it was designed for exactly for
what you are trying to do and is impervious to AvGas.

Gary

Dan_thomas_nos 2009-08-20 15:29:00

I’ve fixed small leaks of fuel and oil using Loctite 290. It’s a
green, wicking-type fluid that penetrates weld pores and so on and
hardens to form a heat-resistant seal. Good place to use it is on the
valve pushrod tubes in the heads of the small Continentals.
But the joint has to be clean and dry. I use lacquer thinner or
brake cleaner to rinse the joint, and blow it out, several times.

Dan

Sbjknox 2009-08-20 15:29:03

Yes. Some years ago a sharp rock punctured a small hole in the bottom
of the fuel tank in my wife’s car. I repaired it with JB Weld and it
is still sealed. I also use JB Weld in the capacitance fuel probe for
my Velocity. And on the radiator top tank in my wifes car.
Two important surface preparation requirements for a long-term fix:
1) Clean
2) Rough
First clean it well with MEK or lacquer thinner before doing and
sanding else you sand the dirt/oil into the roughness. Then scrape
and sand as appropriate to get a rough surface. Then clean again.
Repeat if needed.

Force the JB Weld into the surface roughness with your fingers
(protected by vinyl gloves or the magic “invisable glove” paste eases
clean-up) or a popsicle stick ground off straight on one end.
One thing nice about JB Weld is that it is self-leveling on a
horizontal surface but this will be a problem on a surface with any
slope as the JB Weld will tend to sag to the low side. What I do is
mix a little chopped fiberglass (use scisors to chop it into 2 to 3 mm
lengths). This gives it some “body” and also makes a stronger patch.